Protease inhibitors inhibit carcinogenesis in two-stage carcinogenesis on mouse skin. The inhibition of this carcinogenesis will be probed further. In last year's work we noted inhibition of carcinogenesis initiated by Nitroquinoline-N-oxide promoted by phorbol-myristate-acetate by feeding a diet containing raw soybeans. We noted increased concentration of trypsin inhibitor in the mouse epidermis in the group of animals fed the soybean diet. The presence of soybean trypsin inhibitor (SBTI) in the mouse epidermis will be studied further with the aid of antibodies to SBTI. Inhibition of carcinogenesis by feeding the soybean diet of liver and breast cancer in rats will be attempted. The proteases responsible for induction of mutagenesis in E. coli will be studied.